To enable patterns whose critical dimension is less than 50 nm to be etched, methods for correcting increasingly complex optical distortions have to be incorporated in the optical photolithography methods both at the mask design and production stage and at the exposure stage. The costs of the equipment and of the developments for a new technology generation increase accordingly in very high proportions. These days, the critical dimensions that can be accessed in photolithography are greater than or equal to 65 nm. The 32-45 nm generation is currently in development and there is no viable solution foreseen for the technological nodes less than 22 nm. For its part, electron-beam lithography now allows for the etching of 22 nm patterns; it does not require any mask and offers a fairly short development time, which guarantees a better responsiveness and flexibility in the production of enhancements of the technologies and of the designs. On the other hand, the production times are structurally substantially higher than in photolithography since an exposure has to be produced in steps (with a “stepper”), whereas photolithography requires only a layered exposure. For the designs with repetitive patterns such as memory circuits and gate arrays, a cell projection technology has been developed in which a complete pattern (or cell) is etched in a single shot. A method of this kind is described in U.S. Pat. No. 5,808,310.
In this cell projection technology, the technology expert repeatedly comes up against the problem of reducing the writing time and therefore the number and the duration of the shots in order to reduce the time and the cost of production of a component.